1,3,4-thiadiazin-2-ones

ABSTRACT

Novel heterocyclic compounds of the formula: ##STR1## wherein either X is --CR 1  R 2  -- and Y is oxygen, sulphur or --NR 3  --, wherein R 1 , R 2  and R 3 , which may be the same or different, each is hydrogen or alkyl of up to 4 carbon atoms; or X is oxygen, sulphur or --NH-- and Y is --CH 2  --; wherein R 4  and R 5 , which may be the same or different, each is hydrogen, cyano, nitro, amino or hydroxy, or alkylthio of up to 4 carbon atoms, or has various other meanings defined in claim 1, provided that R 4  and R 5  are not both hydrogen; or wherein R 4  and R 5  are joined together such that with the benzene ring A they form a benzheterocyclic ring as defined in claim 1; and therein the benzene ring A may optionally bear one or more further substituents; or a salt thereof where appropriate. 
     These compounds possess cardiotonic properties, and some of them possess peripheral vasodilator properties, and they are useful for the treatment of acute or chronic heart failure. Representative of the compounds is N,N-dimethyl-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzamide. Also disclosed are processes for the manufacture of the compounds and pharmaceutical compositions containing them.

This is a division of application Ser. No. 528,103, filed Aug. 31, 1983, now U.S. Pat. No. 4,503,054, which is a division of Ser. No. 321,899, filed Nov. 16, 1981, now U.S. Pat. No. 4,423,045.

This invention relates to new heterocyclic compounds which possess cardiotonic properties.

Many 6-aryl-dihydropyridazin-3-one derivatives are known which possess pharmaceutical properties affecting the cardiovascular system. These are described, for example, in the Journal of Medicinal Chemistry, 1974, 17, 273-286 and in the Journal of Heterocyclic Chemistry, 1974, 11, 755-761, and there is much related patent literature.

When an additional hetero-atom is inserted into the pyridazine nucleus, most of the simple structures have been described in the academic chemical literature. Thus, for example:

2-phenyl-4H,6H-1,3,4-thiadiazin-5-one and its 6-methyl analogue are known from Chemical Abstracts, 1948, 42, 5919 and 1956, 50, 7817;

5-phenyl-3H,6H-1,3,4-thiadiazin-2-one and its 6-methyl analogue are known from Leibig's Annalen der Chemie, 1977, 791 and from this article are also known the corresponding p-bromophenyl and 4-biphenylyl analogues;

2-phenyl-4H,6H-1,3,4-oxadiazin-5-one is known from Receuil des Travaux chimiques des Pays Bas, 1929, 48, 417 and o-hydroxyphenyl analogues thereof are known from J.Heterocyclic Chemistry, 1970, 7, 927;

3-phenyl-4,5-dihydro-5-methyl-1H-1,2,4-triazin-6-one is known from J. Heterocyclic Chemistry, 1978, 15, 1271;

6-phenyl-4,5-dihydro-2H-1,2,4-triazin-3-one and its 4-methyl analogue are known from Chemical Abstracts, 1970, 73, 35334.

From the patent literature 5-phenyl-3H,6H-1,3,4-oxadiazin-2-one and the corresponding 4-bromophenyl and 2-naphthyl analogues are known as blowing agents in the plastics industry, from U.S. Pat. Nos. 4,097,425, 4,105,848 and 4,158,094.

None of the abovementioned references discloses any pharmacological utility for any of the compounds described. The only references to pharmacological activity in this kind of compound of which applicants are aware appear in U.S. Pat. No. 3,514,455, which describes various 4,6-disubstituted-2-phenyl-4H,6H-1,3,4-thiadiazin-5-one derivatives which are claimed to possess antipyretic, analgesic, antiinflammatory and antiedema activities, and in U.S. Pat. No. 3,946,010, which describes various 3-o-aminophenyl-4,5 dihydro-1H-1,2,4-triazine-6-one derivatives which are claimed to possess antiinflammatory activity.

A compound of considerable interest at present as a cardiotonic agent is a pyridone derivative known by the name AMRINONE, which has the structure: ##STR2##

We have now found that various phenylthiadiazinone, oxadiazinone or triazinone derivatives which bear a substituent in the 3- or 4-position of the phenyl nucleus possess valuable cardiotonic properties.

According to the invention there is provided a heterocyclic compound of the formula: ##STR3## wherein either X is --CR¹ R² -- and Y is oxygen, sulphur or --NR³ --, wherein R¹, R² and R³, which may be the same or different, each is hydrogen or alkyl of up to 4 carbon atoms;

or X is oxygen, sulphur or --NH-- and Y is --CH₂ --;

wherein R⁴ and R⁵, which may be the same or different, each is hydrogen, cyano, nitro, amino or hydroxy, or alkylthio of up to 4 carbon atoms, or has the formula: ##STR4## wherein Q is a direct link, or is imino (--NH--), or is oxyalkylene of up to 4 carbon atoms, wherein Z is oxygen or sulphur and wherein R⁶, R⁷, R⁸ and R⁹, which may be the same or different, each is hydrogen, alkyl, alkenyl, cycloalkyl or alkoxyalkyl each of up to 6 carbon atoms, or aryl or arylalkyl each of up to 12 carbon atoms, or wherein R⁷ and R⁸ together with the adjacent nitrogen atom form a 5- or 6-membered fully-saturated heterocyclic ring, provided that R⁴ and R⁵ are not both hydrogen;

or wherein R⁴ and R⁵ are joined together such that with the benzene ring A they form a benzheterocyclic ring wherein the heterocyclic part is a 5- or 6-membered ring containing one oxygen, sulphur or nitrogen atom, and which heterocyclic part may optionally contain an oxo substituent or an alkyl or alkanoyl substituent each of up to 6 carbon atoms;

and wherein the benzene ring A may optionally bear one or more further substituents;

or a salt thereof where appropriate.

A suitable value for R¹, R² or R³ when it is alkyl is, for example, methyl or ethyl

A suitable value for R⁴ or R⁵ when it is alkylthio is, for example, methylthio or ethylthio.

A suitable value for Q when it is oxyalkylene is, for example, oxymethylene.

A suitable value for R⁶, R⁷, R⁸ or R⁹ when it is alkyl, alkenyl, cycloalkyl or alkoxyalkyl is, for example, methyl, ethyl, n-propyl, isopropyl, isobutyl, n-hexyl, allyl, cyclopentyl, cyclohexyl or methoxymethyl.

A suitable value for R⁶, R⁷, R⁸ or R⁹ when it is aryl or aralkyl is, for example, phenyl, tolyl, chlorophenyl, trichlorophenyl, benzyl or phenylethyl.

A suitable value for the heterocyclic ring formed by R⁷, R⁸ and the adjacent nitrogen atom is, for example, the pyrrolidino, piperidino or morpholino ring.

A suitable benz-heterocyclic ring formed by R⁴, R⁵ and the benzene ring A is, for example, the benzodioxole, indole, N-acetyl-2,3-dihydroindole or 2-oxo-2,3-dihydroindole ring.

Suitable optional further substituents in the benzene ring A, apart from the essential substituent(s) R⁴ and/or R⁵, are, for example, one or more chloro, bromo, methyl, ethyl, methoxy or ethoxy substituents.

An appropriate salt is a base-addition salt, for example an alkali metal, ammonium or amine salt, for example the sodium, potassium or benzylamine salt, of a heterocyclic compound of the invention wherein R⁶ is hydrogen.

One preferred heterocyclic compound of the invention has the formula given above wherein either X is --CH₂ -- and Y is --NH--, or X is --CH₂ --, --CHCH₃ -- or --C(CH₃)₂ and Y is sulphur, or X is oxygen or sulphur and Y is --CH₂ --, wherein R⁴ has the formula --COOR⁶ or --CONR⁷ R⁸ wherein R⁶, R⁷ and R⁸ have the meanings stated above (that is, wherein Q is a direct link), wherein R⁵ is hydrogen and wherein ring A bears no further substituent. A particularly preferred heterocyclic compound of this type is one wherein X is --CH₂ -- and Y is --NH--, or wherein X is sulphur and Y is --CH₂ --.

A second preferred heterocyclic compound of the invention has the formula given above wherein either X is --CH₂ --, --CHCH₃ -- or --C(CH₃)₂ and Y is sulphur, or X is --CH₂ and Y is oxygen, --NH-- or --NCH₃ --, or X is oxygen, sulphur or --NH-- and Y is --CH₂ --, wherein R⁴ is hydrogen, wherein R⁵ is cyano and wherein ring A bears no further substituent.

Specific heterocyclic compounds of the invention are hereinafter described in the Examples. Of these, preferred compounds are p-(5,6-dihydro-5-oxo-4H-1,3,4,thiadiazin-2-yl)benzoic acid and the methyl and isopropyl esters thereof; p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzamide, N-methylbenzamide and N,N-dimethylbenzamide; p-(5,6-dihydro-5-oxo-4H-1,3,4-oxadiazin-2-yl)benzamide; 6-m-cyanophenyl-4,5-dihydro-1,2,4-triazin-3(2H)-one; p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)benzamide, N-methylbenzamide, N-ethylbenzamide and N-n-propylbenzamide; 3-p-cyanophenyl-4,5-dihydro-1,2,4-triazin-6(1H)-one, p-(2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)benzamide and N,N-dimethylbenzamide; and isopropyl p-(2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)benzoate; and of these a particularly preferred compound is N,N-dimethyl-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzamide.

A preferred process for the manufacture of a compound of the invention wherein X is oxygen or sulphur and Y is --CH₂ -- comprises the reaction of a hydrazide or thiohydrazide of the formula: ##STR5## wherein R⁴, R⁵ and A have the meanings stated above and X is sulphur or oxygen, with an acid of the formula:

    Hal--CH.sub.2 --COOH

wherein Hal is a halogen atom, for example the chlorine or bromine atom, or with a reactive derivative thereof.

When X is sulphur the acid is preferably used directly, and the reaction may be carried out in aqueous solution, in the presence of a base, for example sodium hydroxide, at laboratory temperature.

When X is oxygen the acid is preferably used as a reactive derivative thereof, for example the acyl halide, and the reaction carried out in two stages. The benzoylhydrazine may be reacted with the acyl halide in an inert solvent, for example toluene, in the presence of a base, for example potassium carbonate. The diacyl hydrazine thus obtained may then be reacted with a base, for example sodium hydride, in a dipolar aprotic solvent, for example dimethylformamide, or with an alkali metal carbonate in acetone, and the reaction may be carried out at an elevated temperature, for example at about 100° C.

A preferred process for the manufacture of a compound of the invention wherein X is --CR¹ R² -- and Y is sulphur comprises the reaction of a phenacyl halide of the formula: ##STR6## wherein R¹, R², R⁴, R⁵, A and Hal have the meanings stated above, with a thiocarbazate of the formula:

    H.sub.2 N.NH.CS--O--R.sup.10 or H.sub.2 N.NH.CSO.sup.- M.sup.+

wherein R¹⁰ is alkyl of up to 4 carbon atoms, for example methyl or ethyl, and wherein M⁺ is an alkali metal or ammonium ion.

The reaction may be carried out in an organic diluent or solvent, for example acetonitrile or ethanol, at an elevated temperature, for example at the boiling point of the diluent or solvent.

A preferred process for the manufacture of a compound of the invention wherein X is --CR¹ R² -- and Y is oxygen comprises the cyclisation of a compound of the formula: ##STR7## wherein A, R¹, R², R⁴, R⁵ and R¹⁰ have the meanings stated above. The cyclisation may be carried out in the presence of a base, for example sodium ethoxide, in a diluent or solvent, for example ethanol, at laboratory temperature.

The starting material for the last-mentioned reaction may be obtained by the reaction of a compound of the formula: ##STR8## wherein A, R¹, R², R⁴ and R⁵ have the meanings stated above, with an alkyl carbazate of the formula:

    H.sub.2 N--NH.COOR.sup.10

wherein R¹⁰ has the meaning stated above.

A preferred process for the manufacture of a compound of the invention wherein X is --NH-- and Y is --CH₂ -- comprises the reaction of a compound of the formula: ##STR9## wherein A, R⁴, R⁵ and R¹⁰ have the meanings stated above (the two R¹⁰ substituents being the same or different alkyl radicals of up to 4 carbon atoms), with hydrazine.

The reaction may be carried out in a diluent or solvent, for example ethanol, at a temperature up to the boiling point of the diluent or solvent.

The starting material for the last-mentioned reaction may be obtained either by the reaction of a compound of the formula: ##STR10## wherein A, R⁴, R⁵ and R¹⁰ have the meanings stated above, with an oxonium trifluoroborate of the formula (R¹⁰)₃ OBF₄ wherein R¹⁰ has the meaning stated above, or by the reaction of a compound of the formula: ##STR11## wherein A, R⁴, R⁵ and R¹⁰ have the meanings stated above, with a salt of a glycine ester of the formula H₂ NCH₂ COOR¹⁰, wherein R¹⁰ has the meaning stated above.

A preferred process for the manufacture of a compound of the invention wherein X is --CR¹ R² -- and Y is --NH-- comprises the reaction of a compound of the formula: ##STR12## wherein A, R¹, R², R⁴, R⁵ and R¹⁰ have the meanings stated above, with hydrazine.

The reaction may be carried out in a diluent or solvent, for example ethanol or isopropanol, at a temperature up to the boiling point of the diluent or solvent.

The starting material for the last-mentioned process may be obtained by the reaction of a compound of the formula: ##STR13## wherein A, R¹, R², R⁴ and R⁵ have the meanings stated above, with a chloroformate of the formula R¹⁰ OCOCl, wherein R¹⁰ has the meaning stated above.

A compound wherein R⁴ or R⁵ is an amino substituent may be obtained by the the reduction of the corresponding compound wherein R⁴ or R⁵ is a nitro substituent or by the hydrolysis of the corresponding compound wherein Q is imino.

A compound wherein R⁴ or R⁵ is a carboxy substituent may be obtained by the hydrolysis of the corresponding compound wherein R⁴ or R⁵ is an alkoxycarbonyl or aminocarbonyl substituent.

A compound wherein R⁴ or R⁵ is a carboxy, carbamoyl or thiocarbamoyl substituent may be obtained by the hydrolysis, or reaction with hydrogen sulphide, of the corresponding compound wherein R⁴ or R⁵ is a cyano substituent.

A compound wherein R⁴ or R⁵ is a Q-containing substituent wherein Q is imino may be obtained by the acylation, or reaction with an isocyanate, of the corresponding amino-substituted compound.

A compound wherein R⁴ or R⁵ has the formula --Q--CZ--OR⁶ or --Q--CZ--NR⁷ R⁸, wherein Q is a direct link and Z is oxygen, may be obtained by the reaction of the corresponding compound wherein R⁴ or R⁵ is carboxy or an activated derivative thereof with an alcohol of the formula R⁶ OH or an amine of the formula HNR⁷ R⁸.

A compound wherein R⁴ or R⁵ has the formula --Q--CZ--OR⁶ or --Q--CZ--NR⁷ R⁸ wherein Q is oxyalkylene may be obtained by the reaction of the corresponding compound wherein R⁴ or R⁵ is hydroxy with a compound of the formula Hal--alk--CZ--OR⁶, wherein Hal is a halogen atom and --alk-- is an alkylene group of up to 4 carbon atoms, optionally followed by the conversion of the --CZ--OR⁶ group to --CZ--NR⁷ R⁸ by reaction with an amine of the formula NHR⁷ R⁸.

A compound wherein R³ is alkyl may be obtained by the alkylation of the corresponding compound wherein R³ is hydrogen.

As stated above, a heterocyclic compound of the invention posesses cardiotonic activity. This may be demonstrated by its ability to increase the rate of change of aortic blood pressure in the anaesthetised cat. At a dose of the compound which produces an effective increase in said rate of change, that is, greater than a 25% increase, no symptom of toxicity is apparent.

Some of the heterocyclic compounds of the invention also possesses peripheral vasodilator activity, as demonstrated by their ability to increase the rate of flow in a perfused dog hind limb preparation.

The heterocyclic compound of the invention may be administered to warm-blooded animals, including man, in the form of a pharmaceutical composition comprising as active ingredient at least one heterocyclic compound of the invention in association with a pharmaceutically-acceptable diluent or carrier therefor.

A suitable composition is, for example, a tablet, capsule, aqueous or oily solution or suspension, emulsion, injectable aqueous or oily solution or suspension, dispersible powder, spray or aerosol formulation.

The pharmaceutical composition may contain, in addition to the heterocyclic compound of the invention, one or more drugs selected from sedatives, for example phenobarbitone, meprobamate, chlorpromazine and benzodiazepine sedative drugs, for example chlordiazepoxide and diazepam; vasodilators, for example hydralazine, glyceryl trinitrate, pentaerythritol tetranitrate andd isosorbide dinitrate; diuretics, for example chlorothiazide, hydrochlorothiazide, amiloride, bendrofluazide or chlorthalidone; cardiac membrane stabilising agents, for example guinidine; agents used in the treatment of Parkinson's disease and other tremors, for example benzhexol; and cardiotonic agents, for example digitalis preparations.

When used for the treatment of acute or chronic heart failure in man, it is expected that the heterocyclic compound would be given to man at a total oral dose of between 100 mg. and 2000 mg. daily, at doses spaced at 6-8 hourly intervals, or at an intravenous dose of between 5 mg. and 100 mg.

Preferred oral dosage forms are tablets or capsules containing between 50 and 500 mg, and preferably 100 mg. or 500 mg., of active ingredient. Preferred intravenous dosage forms are sterile aqueous solutions of the heterocyclic compound containing between 0.05% and 1% w/w of active ingredient, and more particularly containing 0.1% w/v of active ingredient.

The invention is illustrated but not limited by the following Examples:

EXAMPLE 1

Bromoacetic acid (6.95 g.) was added to a stirred mixture of p-acetamidothiobenzohydrazide (10.45 g.) and aqueous 2N-sodium hydroxide solution (50 ml.), and the mixture was stirred at laboratory temperature for 75 minutes and then filtered through a filter aid. The filtrate was acidified to pH4 with acetic acid and the mixture was filtered. The solid product was crystallised from aqueous methanol and there was thus obtained N-[p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)phenyl]acetamide, m.p. 266°-267° C.

The p-acetamidothiobenzohydrazide used as starting material was obtained as follows:

A stirred mixture of p-acetamidobenzaldehyde (57.0 g.), piperidine (52.5 ml.) and sulphur (flowers, 16.8 g.) was heated under reflux for 15 minutes. Further piperidine (40 ml.) was added and the mixture was stirred and heated under reflux for 1 hour and then poured into a mixture of ice and water. The mixture was filtered and the solid product was dried and crystallised from ethanol. There was thus obtained (p-acetamidothiobenzoyl)piperidine, m.p. 201°-202° C.

A mixture of the above compound (52.4 g.), chloroform (200 ml.) and bromoacetic acid (29.2 g.) was kept at laboratory temperature for 18 hours and then filtered. There was thus obtained as solid residue N-(p-acetamido-α-carboxymethylthiobenzylidene)piperidinium bromide, m.p. 123° C. (with decomposition).

Hydrogen sulphide was passed during 4 hours through an ice-cooled solution of the above compound (80.1 g.) in ethanol (250 ml.), and the mixture was kept at laboratory temperature for 18 hours and then poured slowly into ice-water (2 liters). The mixture was filtered and there was thus obtained as solid residue carboxymethyl p-acetamidodithiobenzoate, m.p. 224°-226° C.

Hydrazine hydrate (7.5 ml.) was added to a solution of the above compound (40.35 g.) in aqueous 2N-sodium hydroxide solution (75 ml.) and the mixture was kept at laboratory temperature for 30 minutes and then filtered. There was thus obtained as solid residue p-acetamidobenzthiohydrazide, m.p. 220°-221° C.

EXAMPLE 2

The procss described in Example 1 was repeated using the appropriate thiobenzohydrazide as starting material. There were thus obtained the compounds shown in the following table:

    ______________________________________                                          ##STR14##                                                                                                   Crystallisation                                  R.sup.4  R.sup.5   m.p. (°C.)                                                                         Solvent                                          ______________________________________                                         H        nitro     165-167    ethanol/petroleum                                                              ether                                            hydroxy  H         288-289    dimethylformamide/                                                             diethyl ether                                    H        hydroxy   215-217    ethanol                                          amino    H         192-197    ethanol/petroleum                                                              ether                                            H        cyano     193-197    ethanol                                          carboxy  H         306-308 (d)                                                                               dimethylformamide/                                                             diethyl ether                                    dimethyl-                                                                               H         208        isopropanol                                      carbamoyl                                                                      ______________________________________                                    

The starting thiohydrazides were prepared by a similar process to that described in the second part of Example 1. Intermediates that were characterised by melting point are shown in the tables below:

    __________________________________________________________________________                ##STR15##                                                                                       ##STR16##                                          R.sup.4                                                                              R.sup.5                                                                            m.p. (°C.)                                                                               m.p. (°C.)                                   __________________________________________________________________________     H     nitro                                                                              81-83                                                                hydroxy                                                                              H   169-170          179-180                                             amino*                                                                               H   162-164                                                              H     cyano                                                                              71-73            166-168                                             carboxy                                                                              H   222-223          198-199                                             dimethyl-                                                                            H   158              168                                                 carbamoyl                                                                      __________________________________________________________________________      *Prepared by reduction of the corresponding 4nitro compound (m.p.              164-167° C.) with aqueous ethanolic sodium sulphite solution at         80° C.                                                            

    __________________________________________________________________________                ##STR17##                                                                                        ##STR18##                                         R.sup.4                                                                              R.sup.5                                                                            m.p. (°C.) m.p. (°C.)                                  __________________________________________________________________________     hydroxy                                                                              H   193-197              203-205 (d)                                     amino H   127-130           168-169                                            H     cyano                                                                              113                                                                  carboxy                                                                              H   218-221           >310                                               dimethyl-                                                                            H   158                                                                  carbamoyl                                                                      __________________________________________________________________________

EXAMPLE 3

Phenyl chloroformate (6.89 g.) was added to a solution of 2-p-aminophenyl-4H,6H-1,3,4-thiadiazin-5-one (Example 2; 8.28 g.) in pyridine (40 ml.) and the mixture was kept at laboratory temperature for 1 hour, diluted with water and extracted with ethyl acetate. The extract was washed with water, dried and evaporated to dryness and the oily residue was stirred with petroleum ether. There was thus obtained 2-p-(phenoxycarboxyamido)phenyl-4H,6H-1,3,4-thiadiazin-5-one, m.p. 138°-142° C. A mixture of the above compound (3.27 g.), morpholine (1.0 g.) and dioxane (25 ml.) was heated at 100° C. for 2.5 hours, cooled and filtered, and the filtrate was slowly diluted with diethyl ether. The mixture was filtered and the solid product was crystallized from dioxane. There was thus obtained 4-[N-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)phenylcarbamoyl]morpholine, m.p. 268°-269° C.

EXAMPLE 4

Methyl isocyanate (2 ml.) was added slowly to a solution of 2-p-aminophenyl-4H,6H-1,3,4-thiadiazin-5-one (Example 2; 3.1 g.) in boiling ethanol (100 ml.) and the mixture was heated under reflux for 30 minutes, cooled and filtered. There was thus obtained as solid product 1-methyl-3-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)phenylurea, m.p. 275° C.

The process described above was repeated except that the appropriate isocyanate was used in place of methyl isocyanate. There were thus obtained the compounds described in the following table:

    ______________________________________                                          ##STR19##                                                                     R.sup.7     m.p. (°C.)                                                                           Crystallisation Solvent                               ______________________________________                                         ethyl       297-299      dimethylformamide/                                                             diethyl ether                                         n-propyl    250          ethanol                                               allyl       266          ethanol                                               methoxymethyl                                                                              220          dimethylformamide/                                                             diethyl ether                                         ______________________________________                                    

EXAMPLE 5

A mixture of 2-p-hydroxyphenyl-4H,6H-1,3,4-thiadiazin-5-one (Example 2; 10.9 g.), ethyl bromoacetate (8.35 g.), anhydrous potassium carbonate (6.9 g.) and dimethylformamide (50 ml.) was stirred at laboratory temperature for 2 hours and then poured into water. The mixture was extracted with ethyl acetate and the extract was washed with water, dried over magnesium sulphate and evaporated to dryness. The solid residue was crystallised from a mixture of ethyl acetate and petroleum ether, and there was thus obtained ethyl p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)phenoxyacetate, m.p. 142°-144° C.

A mixture of the above compound (2.94 g.), ethanol (10 ml.) and 33% ethanolic methylamine solution (9 ml.) was stirred for 2 hours and then filtered. The solid residue was crystallised from methanol and there was thus obtained N-methyl-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)phenoxyacetamide, m.p. 212°-213° C.

The process described in the second paragraph above was repeated using the appropriate amine in place of methylamine, and there were thus obtained the compounds described in the following table:

    ______________________________________                                          ##STR20##                                                                     R.sup.7 R.sup.8 m.p. (°C.)                                                                         Crystallisation Solvent                             ______________________________________                                         ethyl   H       216-217    methanol                                            n-propyl                                                                               H       202-203    methanol                                            methyl  methyl  199-200    aqueous dimethylformamide                           benzyl  H       192-194    methanol                                            ______________________________________                                    

EXAMPLE 6

A mixture of 2-m-hydroxyphenyl-4H,6H-1,3,4-thiadiazin-5-one (Example 2; 1.0 g.), ethyl bromoacetate (0.61 ml.), ethanol (25 ml.) and sodium hydrogen carbonate (0.84 g.) was heated under reflux for 48 hours and then evaporated to dryness. The residue was dissolved in a 9:1 v/v mixture of chloroform and methanol and chromatographed on silica gel (100 g.) using the same solvent mixture as eluant. The fractions of eluate containing a product having an R_(f) of 0.7 on silica gel plates using the same solvent mixture were combined and evaporated to dryness, and the residue was crystallised from ethanol. There was thus obtained ethyl m-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)phenoxyacetate, m.p. 113°-115° C.

A mixture of the above compound (1.5 g.) and 33% ethanolic methylamine (25 ml.) was heated under reflux for 18 hours and then evaporated to dryness, and the residue was crystallised from a 25:1 v/v mixture of ethanol and dimethylformamide. There was thus obtained N-methyl-m-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)phenoxyacetamide, m.p. 195°-197° C.

EXAMPLE 7

N,N¹ -dicyclohexylcarbodi-imide (19.5 g.) was added to a stirred solution of p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoic acid (Example 2; 21.24 g.), trichlorophenol (20.8 g.) and pyridine (7.25 ml) in ethyl acetate (500 ml.) and the mixture was stirred for 16 hours. Acetic acid (10 ml.) was added, the mixture was filtered and the solid residue was washed well with ethyl acetate. The combined filtrate and washings were evaporated to dryness and the residue was crystallised from a mixture of methanol and dimethylformamide. There was thus obtained 2,4,5-trichlorophenyl p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoate, m.p. 220°-222° C.

A 33% w/v solution of dimethylamine in ethanol (40 ml.) was added to a solution of the above compound (30. g.) in dimethylformamide (150 ml.) and the mixture was kept at laboratory temperature for 1 hour and then diluted with water and filtered. The solid product was dried and crystallised from isopropanol and there was thus obtained N,N-dimethyl-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzamide, m.p. 208° C.

The process described above was repeated using the appropriate amine in place of dimethylamine, and there were thus obtained the compounds described in the following table:

    ______________________________________                                          ##STR21##                                                                                                    Crystallisation                                 R.sup.7   R.sup.8  m.p. (°C.)                                                                          Solvent                                         ______________________________________                                         H         H        268-270     isopropanol                                     methyl    H        236-237     ethanol                                         ethyl     H        222-224     methanol                                        n-propyl  H        236-237     ethanol/diethyl                                                                ether                                           allyl     H        227-229     isopropanol                                     benzyl    H        219-220     isopropanol                                     cyclohexyl                                                                               H        245-246     isopropanol                                     methyl    ethyl    125-126     (purified by                                                                   chromatography)                                 ethyl     ethyl    154-155     isopropanol                                     (CH.sub.2).sub.2O(CH.sub.2).sub.2                                                             180-181     ethanol                                             (CH.sub.2).sub.5                                                                              163-166     methanol                                            ______________________________________                                    

EXAMPLE 8

A mixture of p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoic acid (Example 2; 0.5 g.), concentrated sulphuric acid (0.25 ml.) and isopropanol (100 ml.) was heated under reflux for 36 hours, concentrated by distilling off 70 ml. of the isopropanol, cooled and filtered. The solid residue was crystallised from methanol and there was thus obtained isopropyl p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoate, m.p. 141°-143° C.

The process described above was repeated using the appropriate alcohol in place of isopropanol, and there were thus obtained the compounds described in the following table:

    ______________________________________                                          ##STR22##                                                                     R.sup.6    m.p. (°C.)                                                                        Crystallisation Solvent                                   ______________________________________                                         methyl     205-206   methanol                                                  n-propyl   148-150   methanol                                                  ______________________________________                                    

EXAMPLE 9

A mixture of p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoic acid (Example 2; 1.18 g.) 1-hydroxybenzotriazole (0.72 g.), aniline (0.47 g.) and dimethylformamide (25 ml.) was stirred at laboratory temperature for 45 minutes, dicyclohexylcarbodi-imide (1.6 ml.) was added and the mixture was stirred at laboratory temperature for 15 hours and then evaporated to dryness under reduced pressure. The residue was stirred with diethyl ether, the mixture was filtered and the solid residue was crystallised from ethanol. There was thus obtained N-phenyl-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzamide, m.p. 264°-266° C.

The process described above was repeated except that n-butanol or isobutanol was used in place of aniline. There were thus obtained n-butyl p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoate, m.p. 185°-188° C. after crystallisation from ethyl acetate/diethyl ether, and isobutyl p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoate, m.p. 166°-168° C. after crystallisation from ethyl acetate.

EXAMPLE 10

A mixture of p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoic acid (Example 2; 0.5 g.) and dimethylformamide (30 ml.) was stirred at laboratory temperature for 15 minutes, aqueous 2N-sodium hydroxide solution (1.06 ml.) was added and the mixture was evaporated to dryness. The residue was stirred with methanol, the mixture was filtered and the solid salt was purified by dissolution in water and precipitation from solution with ethanol. There was thus obtained sodium p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoate, m.p. >300° C.

EXAMPLE 11

A mixture of p-amino-2-chloroacetophenone (16.95 g.), methoxythiocarbonylhydrazine (15.9 g.) and acetonitrile (300 ml.) was heated under reflux for 3 hours and then filtered. The filtrate was cooled and filtered, and the solid product was crystallised from acetonitrile. There was thus obtained 5-p-aminophenyl-3H,6H-1,3,4-thiadiazin-2-one, m.p. 233°-235° C.

The process described above was repeated using the appropriately substituted 2-chloroalkanophenone as starting material, and there were thus obtained the compounds described in the following table:

    __________________________________________________________________________      ##STR23##                                                                                        Other Ring A   Crystallisation                              R.sup.1                                                                             R.sup.4  R.sup.5                                                                             Substituent                                                                           m.p. (°C.)                                                                      Solvent                                      __________________________________________________________________________     H    H        cyano                                                                               --     191-192 ethanol                                      H    amino    H    3-chloro                                                                              150-152 isopropanol                                  H    acetamido                                                                               H    --     238     ethanol/                                                                       dimethyl-                                                                      formamide                                    H*   carboxy  H    --     298-300 methanol                                     H*    .sub.--Nmethyl-                                                                        H    --     198-200 methanol                                          carbamoyl-                                                                     methoxy                                                                   H*    .sub.--Nbenzyl-                                                                        H    --     185-188 methanol                                          carbamoyl-           with                                                      methoxy              decomposition                                        H*   carbamoyl                                                                               H    --     255-257 methanol                                     H*   amino    H    3,5-dichloro                                                                          173-175 acetonitrile                                 H*   nitro    H    --     224-226 ethanol                                      methyl                                                                              H        cyano                                                                               --     188-190 methanol                                     methyl                                                                              H        cyano                                                                               2-methyl                                                                              168-169 methanol                                     methyl                                                                              amino    H    --     199-201 acetonitrile                                 methyl*.sup.+                                                                       acetamido                                                                               H    --     201-204 (purified by                                                                   chromatography)                              H    methylenedioxy                                                                               --     119     (purified by                                                                   chromatography)                              H    N(COCH.sub.3)CH.sub.2 CH.sub.2                                                               --     238-245 acetonitrile                                 methyl                                                                              methylenedioxy                                                                               --     121     isopropanol/                                                                   water                                        __________________________________________________________________________      *The corresponding 2bromoalkanophenone was used in place of the                2chloroalkanophenone.                                                          .sup.+ The starting material was obtained as follows: A solution of            pacetamidopropiophenone (1.91 g.) in hot chloroform (10 ml.) was added to      a stirred mixture of finely ground copper (II) bromide (4.01 g.) and ethy      acetate (10 ml.) which was heated under reflux, and the mixture was            stirred and heated under reflux for 3 hours, cooled and filtered. The          filtrate was evaporated to dryness and the residue was stirred with water      The mixture was filtered and the solid product was crystallised from           acetonitrile. There was thus obtained -pacetamido-2-bromopropiophenone,        m.p. 120-121° C.                                                  

EXAMPLE 12

A mixture of S-(1-m-cyanobenzoyl-1-methyl)ethyl thiocarbazate (1.0 g.), concentrated aqueous hydrochloric acid (0.5 ml.) and ethanol (15 ml.) was heated under reflux for 30 minutes and then evaporated to dryness under reduced pressure. The residue was crystallised from ethanol and there was thus obtained 5-m-cyanophenyl-6,6-dimethyl-3H,6H-1,3,4-thiadiazine-2-one, m.p. 140°-142° C.

The thiocarbazate used as starting material was obtained as follows:

A solution of ammonium thiocarbazate (4.9 g.) in a mixture of water (20 ml.) and ethanol (50 ml.) was added to a solution of 1-bromo-1-methylethyl m-cyanophenyl ketone (7.6 g.) in ethanol (10 ml.) and the mixture was stirred at laboratory temperature for 20 hours and then filtered The solid product was crystallised from ethanol and there was thus obtained S-(1-m-cyanobenzoyl-1-methyl)ethyl thiocarbazate, m.p. 179°-181° C. (with decomposition).

EXAMPLE 13

The process described in Example 4 was repeated except that 5-p-aminophenyl-3H,6H-1,3,4-thiadiazin-2-one or the corresponding 6-methyl derivative thereof (Example 11) and the appropriate isocyanate were used as starting materials. There were thus obtained the compounds shown in the following table:

    ______________________________________                                          ##STR24##                                                                     R.sup.7 R.sup.1 m.p. (°C.)                                                                           Crystallisation Solvent                           ______________________________________                                         methyl  H       250-251      ethanol                                           n-propyl                                                                               H       208-210      acetonitrile                                      n-hexyl H       183          ethanol                                           methyl  methyl  222-224      acetonitrile                                      n-propyl                                                                               methyl  215          acetonitrile                                      ______________________________________                                    

EXAMPLE 14

A mixture of 5-p-aminophenyl-3H,6H-1,3,4-thiadiazin-2-one (Example 11; 2.07 g.), methanesulphonyl chloride (1.34 g.) and ethanol (100 ml.) was heated under reflux for 5 hours and then evaporated to dryness under reduced pressure. The residue was stirred with acetonitrile, the mixture was filtered and the solid residue was dissolved in hot dimethylformamide (20 ml.) Acetonitrile was added until crystallisation began, and the mixture was allowed to cool and was then filtered. There was thus obtained as solid product N-[p-2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)phenyl]methanesulphonamide, m.p. 204°-206° C.

The process described above was repeated except that phenylacetyl chloride was used in place of methanesulphonyl chloride, and that the reaction was carried out at laboratory temperature in acetone solution in the presence of triethylamine. There was thus obtained N-[p-(2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)phenyl]phenylacetamide, m.p. 233° C. after crystallisation from acetonitrile.

EXAMPLE 15

A mixture of p-(2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)benzoic acid (Example 11; 0.5 g.) and thionyl chloride (5 ml.) was heated under reflux for 30 minutes and the excess of thionyl chloride was removed by evaporation under reduced pressure. Isopropanol (5 ml.) was added and the mixture was heated under reflux for 30 minutes, cooled and filtered. The solid residue was crystallised from isopropanol and there was thus obtained isopropyl p-(2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)benzoate, m.p. 159°-161° C.

The process described above was repeated using the appropriate alcohol or amine as starting material in place of isopropanol, and there were thus obtained the compounds described in the following tables:

    ______________________________________                                          ##STR25##                                                                     R.sup.6    m.p. (°C.)                                                                        Crystallisation Solvent                                   ______________________________________                                         methyl     194-196   methanol                                                  ethyl      149-151   ethanol                                                   n-propyl   124-126   methanol                                                  isobutyl   158-159   methanol                                                  ______________________________________                                    

    ______________________________________                                          ##STR26##                                                                     R.sup.7 R.sup.8   m.p. (°C.)                                                                        Crystallisation Solvent                            ______________________________________                                         methyl  methyl    218-219   ethanol                                            ______________________________________                                    

EXAMPLE 16

Sodium hydride (500 mg. of a 50% suspension in mineral oil) was added to a solution of N-m-cyanobenzoyl-N¹ -chloroacetylhydrazine (2.3 g.) in dimethylformamide (40 ml.) and the mixture was heated at 100° C. for 2 hours, cooled, diluted with water and acidified to pH 1 with aqueous hydrochloric acid. The mixture was extracted with ethyl acetate and the extract was washed with water, dried and evaporated to dryness. The residue was crystallised from ethyl acetate and there was thus obtained 2-m-cyanophenyl-4H,6H-1,3,4-oxadiazin-5-one, m.p. 229°-230° C.

The diacylhydrazine used as starting material was obtained as follows:

A mixture of ethyl m-cyanobenzoate (10.6 g.) hydrazine hydrate (6.0 ml.) and ethanol (100 ml.) was heated under reflux for 4 hours, cooled and filtered. The solid hydrazide (5.6 g.) was washed with ethanol and dried, and then suspended in toluene (100 ml.). Anhydrous potassium carbonate (4.5 g.) was added to the stirred suspension, followed by chloroacetyl chloride (4.0 g.) added dropwise, and the mixture was stirred for 30 minutes and then washed with water. The toluene solution was then evaporated to dryness and there was thus obtained as residue N-m-cyanobenzoyl-N¹ -chloroacetylhydrazine, which was used without further purification.

EXAMPLE 17

The process described in Example 16 was repeated except that the appropriate ethyl benzoate was used as initial starting material in place of ethyl m-cyanobenzoate, and that dioxan was used as solvent in place of toluene, and triethylamine was used as base in place of potassium carbonate in the preparation of the diacylhydrazine. There were thus obtained the compounds described in the following table:

    ______________________________________                                          ##STR27##                                                                                                     Crystallisation                                R.sup.4   R.sup.5   m.p. (°C.)                                                                          Solvent                                        ______________________________________                                         nitro     H         220-222     ethanol                                        cyano     H         261-264     acetone                                        dimethyl- H         249-254     methanol                                       amino-                                                                         sulphonyl                                                                      H         methylthio                                                                               142-144     methanol                                       H         methane-  218-220     methanol                                                 sulphonyl                                                            H         dimethyl- 202-205     methanol/                                                amino-                petroleum                                                sulphonyl             ether                                          ______________________________________                                    

EXAMPLE 18

A stirred mixture of N-m-methylsulphamoylbenzoyl-N¹ -chloroacetylhydrazine (0.2 g.), potassium carbonate (0.09 g.) and acetone (10 ml.) was heated under reflux for 16 hours and then filtered, and the filtrate was evaporated to dryness. The residue was crystallised from methanol and there was thus obtained N-methyl-m-(5,6-dihydro-5-oxo-4H-1,3,4-oxidazin-2-yl)benzenesulphonamide, m.p. 227°-229° C.

The process described above was repeated using the appropriate diacylhydrazine and there were thus obtained the compounds described in the following table, all of which were crystallised from methanol:

    ______________________________________                                          ##STR28##                                                                     R.sup.4        R.sup.5   m.p. (°C.)                                     ______________________________________                                         H              carbamoyl 278-280                                               H              sulphamoyl                                                                               237-238                                                                        Quarter-hydrate                                       sulphamoyl     H         249-251                                               dimethylcarbamoyl                                                                             H         203-204                                               ______________________________________                                    

EXAMPLE 19

A solution of 2-p-nitrophenyl-4H,6H-1,3,4-oxadiazin-5-one (Example 17; 2.2 g.) in ethyl acetate (250 ml.) was hydrogenated in the presence of a 5% palladium-on-charcoal catalyst at laboratory temperature and atmospheric pressure until 670 ml. of hydrogen had been absorbed. The mixture was filtered and the filtrate was evaporated to dryness. There was thus obtained as solid residue 2-p-aminophenyl-4H,6H-1,3,4-oxadiazin-5-one, m.p. 253°-255° C. (with decomposition).

EXAMPLE 20

The process described in Example 4 was repeated except that 2-p-aminophenyl-4H,6H-1,3,4-oxadiazin-5-one (Example 19) was used as starting material. There was thus obtained 2-p-(3-methylureido)phenyl-4-methyl-3-p-(5,6-dihydro-5-oxo-4H-1,3,4-oxadiazin-2-yl)phenylurea, m.p. 298°-300° C. after crystallisation from ethanol.

EXAMPLE 21

Hydrogen peroxide (2 ml. of a 30% v/v aqueous solution) was added dropwise to a stirred mixture of 2-p-cyanophenyl-4H,6H-1,3,4-oxadiazin-5-one (Example 17; 0.25 g.), anhydrous potassium carbonate (0.86 g.), acetone (12.5 ml.) and water (2.5 ml.) which was kept at 20° C., and the mixture was stirred for a further 18 hours and then filtered. The solid residue was crystallised from methanol and there was thus obtained p-(5,6-dihydro-5-oxo-4H-1,3,4-oxadiazin-2-yl)benzamide, m.p. 295°-298° C.

EXAMPLE 22

Sodium ethoxide (0.5 g.) was added to a stirred solution of 2-hydroxyaceto-(m-cyanophenone) N¹ -ethoxycarbonylhydrazone (0.2 g.) in ethanol (5 ml.) and the mixture was stirred at laboratory temperature for 60 hours and then filtered. The solid product was crystallised from ethyl acetate and there was thus obtained 5-m-cyanophenyl-3H,6H-1,3,4-oxadiazin-2-one, m.p. 204°-208° C.

The 2-hydroxyaceto-(m-cyanophenone) N¹ -ethoxycarbonylhydrazone used as starting material was obtained as follows:

A mixture of m-cyanophenacyl bromide (5.3 g.), potassium acetate (3.47 g.) and acetic acid (30 ml.) was heated under reflux for 2 hours, cooled, diluted with water and extracted with ethyl acetate. The extract was washed with water, dried and evaporated to dryness and the residue was crystallised from ethanol. Concentrated aqueous hydrochloric acid (0.5 ml.) was added to a solution of the 2-acetoxyaceto-(m-cyanophenone) thus obtained (2.5 g.) in methanol and the mixture was heated under reflux for 2 hours and then evaporated to dryness. The residue was stirred with diethyl ether and the mixture was filtered. There was thus obtained as solid residue 2-hydroxyaceto-(m-cyanophenone), m.p. 121°-122° C.

Ethyl carbazate (0.25 g.) and concentrated aqueous hydrochloric acid (0.5 ml.) were added to a solution of the above compound (0.4 g.) in ethanol (20 ml.) and the mixture was stirred for 16 hours at laboratory temperature and then filtered. The solid residue was crystallised from ethyl acetate and there was thus obtained 2-hydroxyaceto-(m-cyanophenone) N¹ -ethoxycarbonylhydrazone, m.p. 146°-147° C.

EXAMPLE 23

A mixture of ethyl p-nitrohippurate (26.5 g.), triethyloxonium fluoroborate (140 ml. of a 2.3 molar solution in methylene chloride) and methylene chloride (400 ml.) was stirred at laboratory temperature for 18 hours. A solution of potassium carbonate (50 g.) in water (50 ml.) was added, the mixture was shaken, and the organic phase was separated, dried and evaporated to dryness. The residue was stirred with petroleum ether and the mixture was filtered. The filtrate was evaporated to dryness and the residual ethyl N-(ethoxycarbonylmethyl)-p-nitrobenzimidate (22.1 g.) was dissolved in ethanol (600 ml.). Hydrazine hydrate (10 ml.) was added and the mixture was heated under reflux for 4.5 hours, cooled and filtered. There was thus obtained as solid product 3-p-nitrophenyl-4,5-dihydro-1H-1,2,4-triazin-6-one, m.p. 284°-286° C.

The process described above was repeated except that the appropriate ethyl hippurate was used as starting material in place of ethyl p-nitrohippurate. There were thus obtained the compounds described in the following table:

    ______________________________________                                          ##STR29##                                                                     R.sup.4                                                                               R.sup.5  m.p. (°C.)                                                                        Crystallisation Solvent                              ______________________________________                                         cyano  H        >300      methanol                                             benzoyl                                                                               H        270-273   n-propanol                                           acetyl H        223-225   (purified by chromatography)                         H      cyano    256-257   methanol                                             ______________________________________                                    

EXAMPLE 24

Dry hydrogen chloride was passed through a mixture of ethyl 2-p-cyanophenoxyacetate (30.75 g.), diethyl ether (500 ml.) and ethanol (10 ml.) at 0°-5° C. until the solution was saturated with hydrogen chloride, and the mixture was kept at 0° C. for 3 days and then filtered. There was thus obtained as solid residue ethyl p-(ethoxycarbonylmethoxy)benzimidate hydrochloride,

m.p. 124°-126° C. A mixture of this compound (6.51 g.), diethyl ether (100 ml.) and a solution of potassium carbonate (3.6 g.) in water (15 ml.) was shaken, the ethereal phase was separated and to it was added a solution of ethyl glycinate hydrochloride (3.1 g.) in water (10 ml.). The mixture was stirred at laboratory temperature for 45 hours and the organic phase was separated, washed with water, dried and evaporated to dryness. The residual oil, which consisted of ethyl N-(ethoxycarbonylmethyl)-p-(ethoxycarbonylmethoxy)benzimidate (5.8 g.) was dissolved in ethanol (75 ml.) hydrazine hydrate (1 ml.) was added and the mixture was heated under reflux for 18 hours and then evaporated to dryness. The residue was purified by chromatography on silica gel using chlorofom containing increasing amounts (up to 5% v/v) of ethanol as eluant. There was thus obtained ethyl p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)phenoxyacetate, m.p. 135° C.

The process described above was repeated using the appropriate ethyl phenoxyacetate in place of ethyl 2-p-cyanophenoxyacetate, and there were thus obtained the compounds described in the following table:

    ______________________________________                                          ##STR30##                                                                                                     Crystallisation                                R.sup.4 R.sup.5       m.p. (°C.)                                                                        Solvent                                        ______________________________________                                         isopropoxy-                                                                            H             233-236   ethanol                                        carbonyl                                                                       H       dimethylcarbamoyl                                                                            218-221   methanol/diethyl                                                               ether                                          H       methoxycarbonyl                                                                              181-183   ethyl acetate                                  methylenedioxy    223-225   ethanol                                            ______________________________________                                    

EXAMPLE 25

The process described in Example 19 was repeated except that 3-p-nitrophenyl-4,5-dihydro-1H-1,2,4-triazin-6-one (Example 23) was used as starting material. There was thus obtained 3-p-aminophenyl-4,5-dihydro-6H-1,2,4-triazin-6-one, m.p. 241°-244° C. after crystallisation from a mixture of dimethylformamide and diethyl ether.

EXAMPLE 26

The process described in Example 4 was repeated except that 3-p-aminophenyl-4,5-dihydro-1H-1,2,4-triazin-6-one (Example 25) was used as starting material. There was thus obtained 1-methyl-3-p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)phenylurea, m.p. 248°-249° C. after crystallisation from ethanol.

EXAMPLE 27

A mixture of 3-p-aminophenyl-4,5-dihydro-1H-1,2,4-triazin-6-one (Example 25; 0.57 g.), acetic anhydride (0.3 ml.) and toluene (50 ml.) was heated under reflux for 90 minutes, cooled and filtered. The solid product was crystallised from ethanol and there was thus obtained N-[p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)phenyl]acetamide, m.p. 300° C.

EXAMPLE 28

The process described in the second part of Example 5 was repeated using ethyl p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)phenoxyacetate (Example 24) and either benzylamine or dimethylamine as starting materials. There were thus obtained N-benzyl-p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)phenoxyacetamide,

m.p. 136°-140° C. after crystallisation from ethanol. and N,N-dimethyl-p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)phenoxyacetamide, m.p. 254°-257° C. after crystallisation from methanol.

EXAMPLE 29

The process described in Example 21 was repeated except that 3-p-cyanophenyl-4,5-dihydro-1H-1,2,4-triazin-6-one (Example 23) was used as starting material. There was thus obtained p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)benzamide, m.p. >300° C. after crystallisation from aqueous acetone.

EXAMPLE 30

A mixture of isopropyl p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)benzoate (Example 24; 0.5 g.), methanol (50 ml.) and 30% w/v methanolic potassium hydroxide solution (1 ml.) was heated under reflux for 30 minutes and then evaporated to dryness. The residue was dissolved in water and the solution acidified to pH 1 with concentrated aqueous hydrochloric acid and then filtered. The solid residue was purified by redissolution in aqueous potassium hydroxide solution and reprecipitation with hydrochloric acid. There was thus obtained p-(1,4,5,6-tetrahydro-6-oxo-1,2,4-triazin-3-yl)benzoic acid, m.p. >300° C.

EXAMPLE 31

A stirred mixture of ethyl N-(2-p-acetamidophenyl-2-oxoethyl)carbamate (2.11 g.), hydrazine hydrate (4 ml.), water (20 ml.) and ethanol (2 ml.) was heated under reflux for 17 hours, cooled and filtered. The solid product was crystallised from ethanol and then from acetic acid, and there was thus obtained N-[p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)phenyl]acetamide, m.p. 280°-284° C. (with decomposition).

The ethyl carbamate used as starting material was obtained as follows:

A solution of bromine (5.83 ml.) in chloroform (40 ml.) was added to a stirred solution of p-acetamido-acetophenone (25.6 g.) in chloroform (200 ml.) and the mixture was stirred for 1 hour and then filtered. The residue was crystallised from isopropanol and there was thus obtained p-acetamidophenacyl bromide, m.p. 182°-184° C.

A solution of sodium azide (40 g.) in water (125 ml.) was added slowly to a stirred solution of the above bromide (56 g.) in dioxan (500 ml.) which was heated to 60° C., and the mixture was stirred and heated at that temperature for 30 minutes. Water (1.2 liters) was added and the mixture was allowed to cool and was then filtered. The solid residue was crystallised from ethanol and there was thus obtained p-acetamidophenacyl azide, m.p. 170° C. (with decomposition).

A mixture of the above azide (14.5 g.), ethanol (100 ml.), chloroform (100 ml.), concentrated aqueous hydrochloric acid (7.5 ml.) and a 30% palladium-on-charcoal catalyst (1 g.) was shaken with hydrogen at laboratory temperature and atmospheric pressure until all the azide had been reduced (the reaction was followed by thin layer chromatography on silica gel plates using a 9:1 v/v mixture of chloroform and methanol as developing solvent). The mixture was filtered and the solid residue was stirred with water (100 ml.). The mixture was filtered and the filtrate was evaporated to dryness. The solid product was crystallised from aqueous ethanol and there was thus obtained 2-(p-acetamidophenyl)-2-oxoethylamine hydrochloride, m.p. 215° C. (with decomposition).

A solution of ethyl chloroformate (6.6 ml.) in diethyl ether (20 ml.) was added to a stirred mixture of the above hydrochloride (14.2 g.), water (80 ml.), pyridine (11.5 ml.) and diethyl ether (20 ml.), and the mixture was stirred for 3 hours and then filtered. The solid product consisted of ethyl N-(2-p-acetamidophenyl-2-oxoethyl)carbamate, m.p. 164°-166° C.

EXAMPLE 32

The process described in Example 31 was repeated except that ethyl N-(2-m-nitrophenyl-2-oxoethyl)carbamate was used as starting material. There was thus obtained 6-m-nitrophenyl-4,5-dihydro-2H-1,2,4-triazin-3-one, m.p. 288° C. (with decomposition) after crystallisation from acetic acid.

The ethyl N-(2-m-nitrophenyl-2-oxoethyl)carbamate used as starting material was prepared from the corresponding 2-m-nitrophenyl-2-oxoethylamine hydrochloride by a similar process to that described in the second part of Example 31. The ethylamine hydrochloride was prepared as follows:

A solution of m-nitrophenacyl bromide (25 g.; m.p. 90°-92° C.; prepared by a similar process to that described in the second part of Example 31) in warm chloroform (95 ml.) was added to a stirred solution of hexamethylenetetramine (15.8 g.) in chloroform (95 ml.) and the mixture was stirred and heated at 50° C. for 4 hours and then cooled and filtered. The solid residue (39 g. after washing with chloroform and drying) was added to a stirred mixture of ethanol (87.5 ml.) and concentrated aqueous hydrochloric acid (42.5 ml.) and the mixture was stirred at laboratory temperature for 17 hours, cooled to a 5° C. and filtered. The solid product was washed with water and then with acetonitrile, and crystallised from methanol. There was thus obtained 2-m-nitrophenyl-2-oxoethylamine hydrochloride, m.p. 215° C. (with decomposition).

EXAMPLE 33

A mixture of methyl N-(2-m-cyanophenyl-2-oxoethyl)carbamate (15.42 g.), hydrazine hydrate (7.07 ml.), water (500 ml.) and ethanol (20 ml.) was heated under reflux for 15 hours, cooled and filtered and the solid product was crystallised from a 4:1 v/v mixture of ethanol and acetic acid. There was thus obtained 6-m-cyanophenyl-4,5-dihydro-2H-1,2,4-triazin-3-one, m.p. 278°-280° C.

The methyl N-(2-m-cyanophenyl-2-oxoethyl)carbamate (m.p. 125°-126° C.) used as starting material was obtained from m-cyanoacetophenone by a similar process to that described in the second part of Example 31 except that methyl chloroformate was used instead of ethyl chloroformate. The following intermediates were characterised by melting point:

m-cyanophenacyl bromide m.p. 67°-69° C.

m-cyanophenacyl azide m.p. 99°-101° C.

2-(m-cyanophenyl)-2-oxoethylamine hydrochloride,

m.p. >360° C.

EXAMPLE 34

The process described in Example 33 was repeated except that the mixture was heated under reflux for only 3 hours and was then cooled and extracted three times with ethyl acetate (100 ml. each time). The combined extracts were dried and evaporated to dryness and the residue was crystallised from ethanol. There was thus obtained methyl N-(2-m-cyanophenyl-2-hydrazinoethyl)carbamate, m.p. 127°-129° C.

A mixture of the above compound (0.5 g.), acetonitrile (5 ml.) and aqueous 2N-sodium hydroxide solution (0.05 ml.) was stirred at laboratory temperature for 3 hours. 33% Aqueous sodium hydroxide solution (0.05 ml.) was added and the mixture was heated at 90° C. for 1 hour, cooled and filtered. The solid residue was crystallised from acetic acid and there was thus obtained 6-m-cyanophenyl-4,5-dihydro-2H-1,2,4-triazin-3-one, m.p. 278°-280° C.

EXAMPLE 35

The process described in Example 33 was repeated except that methyl N-(2-p-cyanophenyl-2-oxoethyl)carbamate was used as starting material in place of the m-isomer. There was thus obtained 6-p-cyanophenyl-4,5-dihydro-2H-1,2,4-triazin-3-one, m.p. 340° C. after crystallisation from dimethylformamide.

EXAMPLE 36

A mixture of N-[p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)phenyl]acetamide (Example 31; 1 g.) and aqueous 4N-hydrochloric acid (15 ml.) was heated under reflux for 25 minutes, cooled and filtered. The residue was dissolved in hot water and the solution was carbon treated, then made basic with aqueous sodium hydroxide solution, cooled and filtered. The solid product was crystallised from water and there was thus obtained 6-p-aminophenyl-4,5-dihydro-2H-1,2,4-triazin-3-one, m.p. 250°-251° C.

EXAMPLE 37

The process described in Example 4 was repeated except that 6-p-aminophenyl-4,5-dihydro-2H-1,2,4-triazin-3-one (Example 36) was used as starting material. There was thus obtained 1-methyl-3-p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)phenylurea, m.p. 337°-340° C. (with decomposition) after crystallisation from acetic acid.

EXAMPLE 38

A mixture of 6-m-cyanophenyl-4,5-dihydro-2H-1,2,4-triazine-3-one (Example 33; 5 g.) and a 30% w/v solution of potassium hydroxide in methanol (30 ml.) was stirred at 55° C. for 20 hours, water (100 ml.) was added and mixture was boiled and then filtered. The hot filtrate was acidified to pH 1 with concentrated aqueous hydrochloric acid and the mixture was filtered. The solid residue was purified by solution in aqueous potassium hydroxide solution and precipitation with concentrated aqueous hydrochloric acid, and was then crystallised from dimethylformamide. There was thus obtained m-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)benzoic acid, m.p. >300° C.

The process described above was repeated except that the corresponding p-cyanophenyl-triazine (Example 35) was used as starting material. There was thus obtained p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)benzoic acid, m.p. 326°-328° C.

EXAMPLE 39

The process described in Example 15 was repeated except that m- or p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)benzoic acid (Example 38) and the appropriate alcohol, amine or ammonia were used as starting materials. There were thus obtained the compounds described in the following tables:

    ______________________________________                                          ##STR31##                                                                             Position of                                                            R.sup.6 Substituent                                                                              m.p. (°C.)                                                                          Crystallisation Solvent                          ______________________________________                                         methyl   .sub.--m-                                                                               212-215     aqueous methanol                                 ethyl    .sub.--m-                                                                               188-191     aqueous methanol                                 n-propyl                                                                                .sub.--m-                                                                               148-150     ethyl acetate                                    methyl   -p-      262-264     ethanol                                          ethyl    -p-      235-237     ethyl acetate/                                                                 diethyl ether                                    isopropyl                                                                               -p-      235-238     methanol                                         ______________________________________                                    

    ______________________________________                                          ##STR32##                                                                                                         Crystal-                                                     Position of       lisation                                   R.sup.7 R.sup.8   Substituent                                                                              m.p. (°C.)                                                                      Solvent                                    ______________________________________                                         H       H          .sub.--m-                                                                               >300    dimethyl-                                                                      formamide/                                                                     diethyl ether                              methyl  H          .sub.--m-                                                                               237-239 methanol                                   ethyl   ethyl      .sub.--m-                                                                               184-186 methanol                                   H       H          -p-      290-295 (d)                                                                            dimethyl-                                                                      formamide/                                                                     methanol                                   methyl  H          -p-      282-284 (d)                                                                            methanol                                   ethyl   H          -p-      310-312 methanol                                   n-propyl                                                                               H          -p-      305-306 (d)                                                                            methanol                                   methyl  methyl     -p-      220-222 methanol                                   CH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2                                                          -p-      245-248 (d)                                                                              aqueous                                                                        methanol                                     ______________________________________                                    

EXAMPLE 40

Hydrogen sulphide was bubbled for 90 minutes through a stirred solution of 6-p-cyanophenyl-4,5-dihydro-2H-1,2,4-triazine-3-one (Example 35; 1.0 g.) and triethylamine (1 ml.) in ethanol (50 ml.) which was maintained at 50° C., and the mixture was then cooled and evaporated to dryness under reduced pressure. The residue was crystallised from dimethylformamide and there was thus obtained p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)thiobenzamide, m.p. 292°-293° C. (with decomposition).

EXAMPLE 41

Sodium hydride (0.72 g. of a 50% dispersion in mineral oil) was added to a stirred solution of 6-m-cyanophenyl-4,5-dihydro-2H-1,2,4-triazin-3-one (Example 33; 3.0 g.) in dimethylformamide (50 ml.), and after the effervesence had ceased a solution of methyl iodide (0.94 g.) in dimethylformamide (5 ml.) was added during 15 minutes. The mixture was stirred for a further hour and then evaporated to dryness under reduced pressure. The residue was purified by chromatography on a silica gel (Merck 7734; 300 g.) column using a 19:1 v/v mixture of methylene chloride and methanol as eluant. There was thus obtained 6-m-cyanophenyl-4,5-dihydro-4-methyl-2H-1,2,4-triazin-3-one, m.p. 248°-251° C. after crystallisation from methanol.

EXAMPLE 42

The process described in Example 10 was repeated using p-(2,3,4,5-tetrahydro-3-oxo-1,2,4-triazin-6-yl)benzoic acid (Example 38) and either aqueous 2N-potassium hydroxide solution or liquid benzylamine as starting materials. There were thus obtained respectively the potassium salt. (m.p. >300° C. after crystallisation from water) and the benzylamine salt (m.p. >300° C. after crystallisation from dimethylformamide) of said acid.

EXAMPLE 43

A mixture of N,N-dimethyl-p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzamide (Example 2; 0.231 g.) and aqueous 2N-sodium hydroxide solution (12 ml.) was stirred at laboratory temperature for 22 hours and then acidified with aqueous 2N hydrochloric acid and filtered. The solid product was crystallised from methanol and there was thus obtained p-(5,6-dihydro-5-oxo-4H-1,3,4-thiadiazin-2-yl)benzoic acid, m.p. 306°-308° C. (with decomposition). 

What we claim is:
 1. A heterocyclic compound of the formula: ##STR33## wherein x is --CR¹ R² -- and Y is sulphur, wherein R¹ and R², which may be the same or different, each is hydrogen or alkyl of up to 4 carbon atoms;wherein R⁴ and R⁵, which may be the same or different, each is hydrogen, cyano, or alkylthio of up to 4 carbon atoms, or has the formula: ##STR34## wherein Q is a direct link, or is imino (--NH--), or is oxyalkylene of up to 4 carbon atoms, where Z is oxygen or sulphur and wherein R⁶, R⁷, R⁸ and R⁹, which may be the same or different, each is hydrogen, alkyl, alkenyl, cycloalkyl or alkoxyalkyl each of up to 6 carbon atoms, or aryl or arylalkyl each of up to 12 carbon atoms, or wherein R⁷ and R⁸ together with the adjacent nitrogen atom form a 5- or 6-membered fully-saturated heterocyclic ring, provided that R⁴ and R⁵ are not both hydrogen; or wherein R⁴ and R⁵ are joined together such that with the benzene ring A they form a benz-heterocyclic ring wherein the heterocyclic part is a 5- or 6- membered ring containing one oxygen, sulphur or nitrogen atom, and which heterocyclic part may optionally contain an oxo substituent or an alkyl or alkanoyl substituent each of up to 6 carbon atoms; and wherein the benzene ring A bears no further substituent or bears one or more chloro, bromo, methyl, ethyl, methoxy, or ethoxy substituents; or a salt thereof where appropriate.
 2. A heterocyclic compound as claimed in claim 1 wherein X is --CH₂ --, --CHCH₃ -- or --C(CH₃)₂ and Y is sulphur;wherein R⁴ has the formula --COOR⁶ or --CONR⁷ R⁸ wherein R⁶, R⁷ and R⁸ have the meanings stated in claim 1, wherein R⁵ is hydrogen and wherein ring A bears no further substituent; or a base addition salt thereof when R⁶ is hydrogen.
 3. A heterocyclic compound as claimed in claim 1 wherein X is --CH₂ --, --CHCH₃ -- or --C(CH₃)₂ and Y is sulphur,wherein R⁴ is hydrogen, wherein R⁵ is cyano and wherein ring A bears no further substituent.
 4. The compound p-(2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)benzamide or N,N-dimethylbenzamide; or isopropyl p-(2,3-dihydro-2-oxo-6H-1,3,4-thiadiazin-5-yl)benzoate.
 5. A pharmaceutical composition possessing cardiotonic properties comprising as active ingredient a cardiotonically effective amount of at least one heterocyclic compound, claimed in claim 1, in association with a pharmaceutically-acceptable diluent or carrier therefor.
 6. A composition as claimed in claim 5 which contains, in addition to the heterocyclic compound, one or more drugs selected from sedatives, vasodilators, diuretics, cardiac membrane stabilising agents, agents used in the treatment of Parkinson's disease and other tremors, and cardiotonic agents.
 7. A method for the treatment of acute or chronic heart failure in a warm-blooded animal in need of such treatment which comprises administering to said animal an effective amount of a heterocyclic compound claimed in claim
 1. 